Stem cell factor (SCF) is a glycoprotein growth factor that acts on haematopoietic blood cell progenitors.12 Whereas SCF alone exerts little colony-stimulating activity on normal human bone marrow cells in vitro, combination of SCF with other recombinant haematopoietic cytokines results in a synergistic increase in numbers of colonies.13 In vivo, the addition of SCF to G-CSF (Filgrastim) synergistically increases PBPC mobilization compared to Filgrastim alone.14-17 Several clinical trials have reported the ability of the combination of SCF with Filgrastim to mobilize PBPC in patients with lymphoma, multiple myeloma, breast and ovarian cancers even in heavily pretreated patients.18-26 Priming using chemotherapy is toxic and costly11 and new priming procedures need to be established, which is the background for this randomized pilot study. The hypothesis is that elimination of chemotherapy from the priming regimen may decrease the overall toxicity and the ability to collect a sufficient autograft which, however, may be circumvented by adding r-metHuSCF (Ancestim) to the priming regimen. The aim of this randomized phase II trial was to evaluate safety, toxicity and efficacy of growth factors in lymphoma patients considered candidates for high dose chemotherapy.